The present invention is directed generally to methods of separating water and solids from oil and gas and more particularly to a wellbore completion design that separates water and solids from oil and gas downhole in such a way that the water and solids remain downhole. These solids will usually consist of granular to very fine sized formation solids, or solids introduced into the well during drilling, completion, stimulation, or production operations.
One of the most burdensome aspects of producing hydrocarbons from a well for well operators is dealing with the presence of solids and water in the hydrocarbons. It is not desirous to have either of these by-products present in the hydrocarbons. Indeed, the presence of these elements in hydrocarbons only inhibits their recovery, often to the degree that economics will force an operator to suspend or even abandon well production. Accordingly, well operators have had to develop techniques for removing or separating the sand and water from the hydrocarbons as nature itself in most wells lends no assistance in this regard. Many of the techniques developed to deal with the removal of these elements, however, are cumbersome, expensive, not always environmentally friendly and often involve complex processes and equipment.
One conventional technique for removing sand from the hydrocarbons is to install sand screens at the end of the production pipe or inside the wellbore through the producing interval. These sand screens typically comprise multiple layers of wire mesh. The pore sizes of these screens are usually selected to filter out or remove as many granules of sand present in a particular formation as possible. Thus, the screens can be, and often are, customized for a particular application. Thus, one screen does not usually “fit all.” Accordingly, well operators are required to learn as much about the nature of the formations they will be producing from to insure that they select the right sand screen to filter out as much of the sand as possible.
There are two major drawbacks to using sand screens for removing sand from hydrocarbons. First, over time the sand screens begin to plug up. This causes a decrease in the amount of hydrocarbons being produced. Eventually, the sand screens plug up entirely, requiring either removal of the sand screen or invocation of an operation to clean the sand screens, downhole. Typically, either operations will require the well to be shut down, which in turn ceases the production of hydrocarbons, and causes an additional economic loss to the well owner. Another major drawback of using sand screens attached to the production tubing is that eventually sand bridges form between the sand screen and the wellbore wall. These sand bridges block the flow of remedial treatment fluids, which occasionally need to be pumped downhole through the annulus between the production tubing and the wellbore. To unblock the sand bridges, the well often has to be shut down so that the sand screen can be removed for cleaning. This again results in an economic loss to the well owner.
Another technique for removing sand and other debris from the hydrocarbons being produced from a well is to employ a device at the surface, known as a separator; in some cases, specifically a sand separator. This technique involves producing the sand with the hydrocarbons. A drawback of this approach, however, is that the separator devices take up space at the surface, which is often limited in off-shore applications. Furthermore, it reduces the producing rate of the well, requires repeated cleaning or maintenance, and may be a separate additional device needed additional to a water separator system.
Water is usually removed from the hydrocarbons at the surface using multi-phase separation devices. These devices operate to agglomerate and coalesce the hydrocarbons, thereby separating them from the water. A drawback of this approach, however, is that no separation process is perfect. As such, some amount of the hydrocarbons always remains in the water. This can create environmental problems when disposing of the water, especially in off-shore applications. Also, the multi-phase separation devices are fairly large in size, which is another disadvantage in off-shore applications, as space is limited as pointed out above. Another limitation is that this can require additional maintenance or repair if solids are part of the produced fluid stream.